The visualization consists of a slider controlling a variable which is also shown in a text output field.

If you want to move one of those sliders on the web page to change a variable you will notice that there is a mismatch of the cursor position and the slider movement.

The further you move down on the screen the bigger the the mismatch i.e. if you position the cursor ona slider you cannot move it - instead, a slider further down the page might move if you happen to get the "right" offset.